This invention pertains to the bonding of optical fibers to Mxc3x97N perforated alignment plates and to methods of making such assemblies into high density optical connectors and optical fanouts.
The bonding of optical fibers into alignment plates fabricated of silicon, silica and other materials is well known. However, the adhesive used in these applications, in particularly for high dimensional precision bonding required of signal-mode optical fiber applications, is typically an organic adhesive generically referred to as an xe2x80x9cepoxy.xe2x80x9d
Epoxies have many advantages for the bonding of dissimilar materials, not the least of which is their low viscosity (important for high dimensional precision, i.e. thin bond line), strength, toughness and ease of application. However, irrespective of cure technique (UV, thermal, etc.), epoxies have modest glass transition temperatures (Tg) in which their mechanical properties are better described as visco-fluidic rather than solid. Unfortunately, the transition between fluidic and solid is more or less a continuum in which the onset of undesirable visco-elastic characteristics of the epoxy can occur at temperatures significantly below that of the Tg.
In the field of high precision bonding of optical fiber, these undesirable visco-elastic characteristics of epoxy can significantly increase the risk of system failure due to fiber misalignment. The high thermal coefficient of expansion (TCE) of epoxies, in particular for temperatures approaching the Tg (typically xcx9c125xc2x0 C.) whereby the TCE in general increases threefold, can cause mechanical reliability concerns of the optical fiber itself.
For these reasons of performance in mechanical reliability, including a lack of hermeticity to the ingress of water through the bondline, the telecommunications industry has experimented with the variety of alternative bonding technologies including glass-to-metal sealing with limited success.
To date, however, a bonding technology that does not exhibit the deleterious effects of visco-elastic creep and non-linear TCE associated with epoxies and the cost and difficulty encountered with glass-to-metal seals, has not yet been found. There is a need to find a method to connect optical fibers into alignment plates which will allow high dimensional precision bonding for single-mode optical fiber applications.
In one respect, the invention comprises a fiber optic assembly including an alignment plate having at least one alignment hole formed thereon and at least one optical fiber. The optical fibers are smaller in diameter than the holes. The each optical fiber is inserted into a respective one of the alignment holes. A bondline is located between each optical fiber and its respective alignment hole. The bondline preferably comprises an inorganic adhesive having a glass transition temperature of at least about 150xc2x0 C.
In another respect, the invention comprises a fiber optic assembly including an alignment plate having at least one alignment hole formed thereon and at least one optical fiber. The optical fibers are preferably smaller in diameter than the holes. Each optical fiber is inserted into a respective one the alignment holes and is bonded thereto along a bondline. The bondline is preferably less than about 200 nm in thickness and comprises a sol-gel having a glass transition temperature of at least about 150xc2x0 C.
In yet another respect, the invention comprises a fiber optic assembly including a plurality of optical fibers bonded to a plurality of holes formed in an alignment plate along a plurality of bondlines by an inorganic adhesive. The bondlines correspond to lines of contact between each of the optical fibers and a respective one holes formed in the alignment plate. The inorganic adhesive is preferably formed from a colloidal suspension of sodium silicate.